Grieving “Jackass” star Bam Margera tattooed Ryan Dunn’s name on his wrist last week. The daredevil hatched the idea while partying at GunBar, in the Meatpacking District, where he was overheard saying that he wanted to “commemorate Dunn” and that, it “would be hard to watch” the new season of “Bam’s World Domination” on Spike TV, which they filmed together. Margera went over designs with GunBar’s in-house artist, but he “ultimately decided to wait until the morning to get the tattoo,” a spy said. Before heading for Europe on Friday, Margera headed to NY Ink at 11 a.m. to get Dunn’s name inside a pre-existing heart tat.